So if this person booked a last minute ticket from AUK-LAX-ATL-MCO in couch, even as a Diamond, there might not have been any C+ seats available for immediate upgrade for them, so they'd be on both C+ and FC lists.. That persons check in window is 24 hours plus the 19 hours difference (relative to LAX, 16 hours ahead relative to MCO) plus the 12+ hour flight to LAX plus the 4 hour to ATL and the 1 hour to MCU, plus all the potential connections that could be 24 hours long (each?). Even with say only 2 hours in between each flight, that's at least 67 hours before the flight that they could be already appropriately on the waiting list